Revert "Temporarily stop using moblab-generic-vm-pre-cq."

This reverts commit ff3fccc5f33ec8344f15d84ca19c18596d0d3e2c.

Reason for revert: This build-config is green again after the workaround.

Original change's description:
> Temporarily stop using moblab-generic-vm-pre-cq.
> 
> This pre-cq config is consistently timing out currently. Let's pull it
> out from the largest user to not impact users until we've fixed the root
> cause(s).
> 
> BUG=chromium:810061
> TEST=None
> 
> Change-Id: Iff1c4b49546153b8922f40c82d731aa5225e3223
> Reviewed-on: https://chromium-review.googlesource.com/907030
> Reviewed-by: Xixuan Wu <xixuan@chromium.org>
> Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>

BUG=chromium:810061

Change-Id: Id2ba43ddfa019bdfc23b3a9519c2e77a1029c07f
Reviewed-on: https://chromium-review.googlesource.com/909749
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Xixuan Wu <xixuan@chromium.org>
diff --git a/COMMIT-QUEUE.ini b/COMMIT-QUEUE.ini
index 37f78fa..7e8c95d 100644
--- a/COMMIT-QUEUE.ini
+++ b/COMMIT-QUEUE.ini
@@ -8,7 +8,7 @@
 [GENERAL]
 
 # Change the default set of PreCQ builders.
-pre-cq-configs: betty-pre-cq
+pre-cq-configs: betty-pre-cq moblab-generic-vm-pre-cq
 
 subsystem:all
 # Allow union of pre-cq configs from subdirectory